As digital color printing demands continue to grow, there is a continuing need for color reproduction improvement. Most color print profiles technologies often focus on color accuracy and smoothness of the color lookup table (LUT).
For a three-ink cyan, magenta and yellow (CMY) printer, the mapping from ink amounts to colorimetric coordinates is unique and various interpolations or fitting techniques can be applied directly. For a four-ink CMYK printer where K represents black ink, redundancy is introduced with the addition of the black ink. Generally a unique color can be produced by one CMY ink combination, whereas there may be many CMYK ink combinations that may produce the same color, depending on the black ink amount. The inverse characterization for a CMYK ink set is generally performed by various methods of controlling the black ink amount. These methods may include black addition, under-color removal (UCR), or gray-component replacement (GCR), which are traceable to the graphic arts printing industry. Generally, the GCR level is determined by checking the graininess of prints or decreasing printing cost by replacing the expensive chromatic colorants with the black colorant.
However, adjusting the black ink using a gray component replacement strategy can negatively affect the color constancy of the print.